Synthesis and characterization of technetium(V) and (VII) complexes with bidentate nitrogen donor ligands. X-ray molecular structures of tetrabutylammonium bis(1,2-diimidobenzene)oxotechnetium(V) and tris(1,2-diimidobenzene)technetium(VII) pertechnetate

Abstract

The reaction of pertechnetate with 1,2-diaminobenzene (H 2pda) in the presence of the reducing agent sodium dithionite in alkaline aqueous solution led to the formation and isolation of (n-Bu 4N)[TcO(pda) 2] ( 1). If the reaction is performed without reducing agent in methanol, the green compound [Tc(pda) 3](TcO 4) ( 2) is formed. Both complexes are diamagnetic, and a single NH stretching frequency in both indicates that each pda ligand contains one hydrogen per nitrogen, and is dianionic. X-ray crystal structures of both compounds are also reported. Crystal data for complex 1, C 28H 48N 5OTc: orthorhombic, space group P2 12 12 1, a=11.644(3), b=15.303(4), c=16.950(5) Å and U=3020.3(1.5) Å 3 to give Z=4 for D calc=1.25 g cm −3. Crystal data for 2, C 18H 18N 6O 4Tc 2: orthorhombic, Pna2 1, a=13.869(4), b=12.799(5), c=10.851(3) Å and U=1926.2(1.1) Å 3 to give Z=4 for D calc=1.99 g cm −3. The structures have been solved by Patterson and Fourier methods and refined by least-squares methods to R=0.058 for 1 and 0.090 for 2. Complex 2 represents the first tris-bidentate cationic complex of technetium to be structurally characterized. Complex 1, with an unexpectedly low ν(TcO) of 891 cm −1, has a TcO bond distance of 1.668(7) Å, that is typical for monooxotechnetium(V) square-pyramidal complexes.